Stable elongated elements and smoking means incorporating the same



April 11, 1967 R. M. BERGERETAL 3,333,306

STABLE ELONGATED ELEMENTS AND SMOKING MEANS INCORPORATING THE SAME Filed Oct. 22, 1965 3 Sheets-Sheet l INVENTORS Richard M. Berger Reavis C. Sproul.

ATTORN EYS Amd M9 E967 R. M. BERGER ETAL @M3939 STABLE ELONGATED ELEMENTS AND SMOKING MEANS NCORPORATING THE' SAME Filed oct. 22, 1965 3 Sheets-Sheet 2 INVENTORS ATTORN EYS 3,313,305 MEANS April 11, 1967 R. M. BERGER ETAL STABLE ELONGATED ELEMENTS AND SMOKING INCORPORATING THE SAME 5 Sheets-Sheet 5 Filed Oct. 22, 1965 Reavis C. Sproull ATTORNEYS United States Patent O 3 313,306 STABLE ELONGATEDELEMENTS AND SMOKING MEANS ENCORPRATING 'Hm SAME Richard M. Berger and Reavis C. Sprouil, Richmond, Va.,

assignors to American Filtrona Corporation, a corporation of New York Filed (ict. 22, 1965, Ser. No. 502,261 8 Claims. (Cl. ll-10.7)

This application is a continuation-in-part of copending applications Ser. Nos. 351,162 and 458,050, filed Mar. 11, 1964, and May 24, 1965, respectively, application Ser. No. 458,050, having now issued as Patent No. 3,217,715 and in turn being a continuation-impart of applications Ser. Nos. 306,343, 343,463, 351,161 and 392,014, filed Sept. 3, 1963, Feb. 10, 1964, Mar. 1l, 1964, and Aug. 25, 1964, respectively, all now abandoned but with the present application having the priority thereof with respect to common subject matter.

This invention relates generally to the production of stable elongated elements, and preferred embodiments hereof are concerned with the provision of elements having as at least a major constituent a substantially continuous filamentary tow of the type which is suitable for use in smoke filters. However, the invention is applicable to different materials, as well as different forms of material as explained below.

The term continuous lamentary tow, as used in this specification and the appended claims, is intended to define a material such as that which results when filaments extruded from a plurality of spinncrets are brought together and combined to form a continuous body of fibers randomly oriented primarily in a longitudinal direction. In such a tow, the filaments are generally longitudinally aligned in substantially parallel orientation, but include crimped portions which may form short sections running more or less at random in non-parallel diverging and converging directions.

y Continuous filamentary tows of plasticized cellulose acetate fibers have been used heretofore in the manu- -facture of smoke filters for cigarettes, cigars and the like. Generally, the fibers of the tow emerging from the spinneret are hunched together to form a raw tow which is collected into a bale for subsequent processing. Such processing usually involves, in addition to unwinding of the raw tow, spreading apart of the fibers to provide a relatively thin layer of the same, tensioning of the fibers to render the crimp of uniform character, impregnating the fibrous layer with a plasticizer to bind adjacent fibers together, and gathering the bonded layer through a suitable funnel or the like to form a treated cylindrical tow which is overwrapped in a suitable paper to produce a stable elongated element. This overwrapped rod is then generally severed into segments which are cured and later cut into substantially equal size filter plugs to be secured to a cigarette or the like by a tipping overwrap in a well-known manner. The curing procedure has ordinarily been commercially effected heretofore by either heating the paper-covered segments in an oven to allow the plasticizer to permanently bond the tow fibers together, or merely by permitting the segments to age for an extended period of time in an unheated condition.

Although satisfactory cigarette filters utilizing the processing techniques described above have been produced, various disadvantages are inherent in such prior operations:

1) Since the filamentary tow is generally not selfsustaining, it is necessary with prior art techniques to overwrap the same with a suitable paper to facilitate further handling and processing of the filter elements. Such a procedure is relatively expensive and produces a product, the pressure-drop and various other characteristics of which cannot be continuously monitored because of the paper overwrap. It is therefore generally necessary to remove samples from the processing line at spaced intervals for such testing. However, with a testing procedure of this type, it can be readily seen that relatively large quantities of unsatisfactory products can be produced while the sample is bein tested, and this can result in a substantial loss of time and material before adjustments can be made in the machinery to correct the deficiencies.

(2) The necessity of a paper overwrap to produce stability renders the severing process not completely satisfactory since the material being cut is not of a substantially uniform character, but rather includes materials of different characteristics, i.e., paper and tow, whereby nonuniformity in the product results and relatively high Wear on the cutter or knife edges.

(3) Since the continuous filamentary tows manufactured according to the prior art overwrap techniques require a paper overwrap to maintain dimensional stability, their subsequent use is limited generally to cigarette filters, the overwrap preventing certain other applications of the product with which the paper interferes,

(4) Since the product is overwrapped with such techniques, an operator cannot examine a rod as it is produced to determine whether or not the plasticizer has been unevenly applied and/or distributed. The rod is covered with paper as cured and those defects known in the trade as soft sides and worm holes do not become apparent for convenient observation so as to permit immediate correction of the deficiency. Additionally, since the product is not finally cured as produced, but instead, must await separate final curing, some of the defects do not become apparent on the production line, as such.

(5) Also, since the products must be cured between high speed production thereof and their ultimate use for example in a cigarette, the prior techniques do not readily lend themselves to automatic material handling arrangements such as, for example, pneumatic conveyors delivering the products from the filter production line directly to the cigarette machine.

Suggestions are found in the prior art for the production of substantially sta-ble tow products, including cigarette filters which do not require an overwrap, but these suggestions each have inherent disadvantages. In `general, prior art attempts in this direction have either been commercially undesirable from the standpoint of increased processing costs, decreased product utility or reduced functional efiiciency and thus, such suggestions have not gained commercial acceptance by the industry. More specifically, with the prior overwrap techniques as well as with prior stable rod techniques, the filamentary tow is pulled through the various processing devices. This pulling results in an undesirable tension on the individual filaments and can provide the product with further dimensional instability whereby changes in size, shape and functional characteristics can be experienced during the curing operation and even during subsequent handling in use. Moreover, relatively uneven elongation of the fibers in the filamentary tow can be caused lby the pulling tension on the same during feeding, particularly since the material is generally quite soft and pliable during processing. Thus, once again, uniform functional properties cannot easily 4be realized at least at very high speeds with such procedures. With other prior stable rod techniques bonding of the filaments has not Ibeen completely satisfactory because the setting or curing steps have failed to evenly and uniformly affect the voverall cross-section of the elongated element whereby insufficient hardness and undesirable pressure-drop characteristics have been encountered in many instances. In this regard, previous attempts to carry, rather than pull, the filamentary tow through the processing stations have been coupled with unsatisfactory heating and curing techniques, e.g., reliance on heat conducted by the carrying means to the tow therewithin resulting in insufficient and uneven heating throughout the cross-section of the tow, whereby, although certain disadvantages were removed, other undesirable features were introduced.

A further area in which the prior art has proven to be somewhat deficient concerns the production of stable elongated elements, particularly smoke filters for cigarettes or the like, wherein various additive materials such as carbon or the like are incorporated either as yan additive or as a discrete section of the product. Frequent attempts have been made to merely disperse such additive materials throughout the tow prior to forming the elongated element, but the procedures utilized in the past have either been unduly expensive, or have resulted in relatively nonuniform intermixtures of the additive with the tow. Moreover, yuntil relatively recent developments exemplified by the aforesaid parent applications, such additives could not be utilized as a predominant structural material within the product. In general, cigarette filtration desiring the incorporation of such an additive has been effected by the use of the well'known dual lter wherein two separate filter elements of different properties were secured to each other in end-toend relationship and then to a tobacco section by a tipping ove-rwrap. Some use has also been made of discrete or loose carbon lpart-icles intermediate a pair of tow filter elements, all of which was secured to the tobacco portion of the cigarette.

It becomes relatively clear from even a brief consideration of such prior art techniques, that the handling of a plurality of individual filter elements, and even more particularly, the handling of loose carbon particles, in the manufacture of a cigarette is complicated and expensive. Thus, although such techniques are in relatively wide commercial yuse because of the great public demand for filter cigarettes, they have numerous undesirable characteristics from a manufacturing standpoint.

While the various techniques and disadvantages of the same described hereinabove are believed to be representative of the manufacturing methods in -most wide-spread use at the lpresent time, it is to be understood that the foregoing is not intended to be comprehensive and, by contrasting the instant inventive concept with prior art procedures, other undesirable features inherent in the latter will be readily recognized.

Bearing in mind the foregoing, a primary object of the present invention is the provision of stable elongated elements which in themselves are free from the various dis- -advantages noted above, and which are manufactured utilizing methods and means not subject to the drawbacks of previously utilized techniques and devices.

More specifically, it is an important object of Kthe present invention to provide a smoke filter .structure having various functional characteristics such as uniformity, ease of handling and testing, filtration eflic-iency, etc., which are superior to products now available on the commercial market. Further, in this regard, it is a basic object of the instant invention to provide for the production of stable continuous elements in a manner which is simple and inexpensive as well as reliable and eicient at high speeds. Accordingly, the present invention is concerned with providing various elongated elements, and in particular, smoke filter rods that can be segmented for use as cigarette filters, cigar filters, or the like, in a continuous, commercially desirable, manner.

Consistent with the above, it is an important object of the present invention to provide a smoke filter, preferably formed primarily from a continuous lilamentary tow, wherein the raw material need not be pulled through the various processing stations, but Irather is carried, substantially in the absence of any tension, from one treating apparatus to the next, by a continuous surface through which the material can be directly processed to form the final product with a minimum of disturbance. In effecting this result, a significant feature of the instant inventive concept is the utilization of an endless belt which is continuously orbited through certain treating zones. The belt is flexible whereby it can be utilized to form the material into a desired shape and the belt is also porous, at least throughout a portion of its length, whereby various gaseous materials such as steam and air can be passed directly into the material being processed while the same is confined and carried in a continuous manner by the belt and without the steam or air being hampered or restricted by the belt in its travel to :and through the material being processed. In this regard, although 4the instant invention is directed basically to the production of a stable elongated element such as a filter rod or the like, having as its predominant structural constituent a continuous filamentary tow, the broad concept of utilizing an endless open mesh porous surface to for-m the material and simultaneously receive gaseous treating substances therethrough without restriction, is equally applicable to the production of a predominantly particulate product such as shown in parent application Serial No. 351,162, is referred to previously. Further, as will be pointed out in more detail hereinafter, it is contemplated that elements having substantially all-tow portions and integral portions formed primarily of particulate material can be produced in this manner. Similarly, the same basic techniques can be utilized for the production of tow-type continuous elements having certain particulate additives substantially uniformly dispersed therethrough.

As mentioned above, one of the primary objectives of this invention is the provision of continuous elements which are stable and self-sustaifning whereby the necessity for overwrapping the same to insure dimensional stability .and facilitate further processing and handling is obviated.

Along the same lines, it is a significant object of this invention to provide a non-wrapped stable elongated element which is fully cured during a continuous processing technique whereby any defects in the product are immediately observable for correction and whereby the products may be automatically fed to subsequent processing apparatus for their ultimate use.

A further important objective of the instant invention is the provision of a stable elongated element the periphery of which is embossed in accordance with the surface configuration of the endless belt utilized to carry andV form the same during the processing of the material. This embossed or textured peripheral surface, in contrast to the relatively smooth peripheries realized with various prior art techniques for making self-sustaining elements of this type, greatly increases the bonding properties of the same when adhesively secured, for example, to a tipping overwrap in the manufacture of a cigarette utilizing a segment of the element as filter plug. Moreover, the embossed peripheral surface of the product of the instant invention improves the stability of the element and precludes fraying of the peripheral surface, .an undesirable characteristic of many prior art products.

Yet another significant object of this invention is the production of a stable elongated element having spaced portions of different characteristic integrally connected by a central core whereby continuity of the product may be effected. In this regard, the instant invention includes the production of dual filters comprising a first section formed essentially of a stable, porous, all-tow element, and a second section having a central core which is a continuation of the tow in the central -portion of the first section `and which has a stable, porous, annular sheath of an additive material bonded together and yto the central core thus yresulting in a one-piece dual filter construc- Y tion.

ments in accordance with the instant invention, certain hidden parts being shown in dotted lies for illustrating clarity;

FIGURE 2 is an enlarged, fragmentary, plan view taken substantially on line 2 2 of FIGURE 1 and showing a portion of the endless, flexible, porous belt utilized for forming and carrying the tow mate-rial through the various processing stations;

FIGURE 3 is an enlarged, transverse cross-sectional view taken substantially on line 3 3 of FIGURE 1 and showing the initial formation of the belt and the guiding of the continuous filamentary tow thereinto;

FIGURE 4 is an enlarged, fragmentary, transverse cross-sectional view taken substantially on line 4 4 of FIGURE l and illustrating the confined zone wherein steam-treatment of the material is effected;

FIGURE 5 is an enlarged, transverse, cross-sectional view taken substantially on `'line 5 5 of FIGURE 1 and showing the somewhat elongated or elliptical shape of the belt and the material therein as the same leaves the steam-treating station;

FIGURE 6 is an enlarged, fragmentary, transverse cross-sectional view taken substantially on line 6 6 of FIGURE l and illustrating the removal of the seam from the steam-treated intermediate element and the simultaneous reforming of the same into its substantially cylindrical final cross-sectional shape;

FIGURE 7 is an enlarged, fragmentary, transverse cross-sectional view taken substantially on line 7 7 of FIGURE 1 and showing the confined zone wherein air cooling of the material is effected;

FIGURE 8 is an enlarged, transverse cross-sectional view taken substantially on line 8 S of FIGURE l and illustrating the final circular cross-sectional shape of the stable elongated product;

FIGURE 9 is a fragmentary, perspective view of the initial forming of the endless belt and the material therein, parts being broken away for illustrative clarity;

FIGURE 10 is an enlarged, fragmentary, perspective view of a cigarette carrying a filter plug made according to the process shown in FIGURE l, parts being broken away for illustrative clarity;

FIGURE 1l is a schematic representation of a preferred method and means for forming dual filter elements according to the instant inventive concept, parts being broken away lfor illustrative clarity and convenience;

FIGURE l2 is an enlarged, fragmentary, elevational view taken substantially on line 12 12 of FIGURE 11 and illustrating a portion of the endless, flexible, partially porous belt utilized in the initial formation of dual filter;

FIGURE 13 is an enlarged, transverse cross-sectional view taken substantially on line 13 13 of FIGURE l1 and showing the intermediate elongated element as the same is being confined for subsequent inclusion of an additive material;

FIGURE 14 is an enlarged, transverse cross-sectional view taken substantially on line 14 14 of FIGURE 11 and illustrative of the intermediate product with the additive material carried thereby;

FIGURE l5 is an enlarged, transverse cross-sectional view taken substantially on line 15 15 of FIGURE 11 and showing the structural characteristics of the additivecontaining portion of the dual filter product; and

FIGURE 16 is an enlarged perspective view of a dual filter formed in accordance with the method of FIGURE 1l, parts being broken away for illustrative clarity.

Like reference characters refer to like parts throughout the several views of the drawings.

Referring now to the drawings in general, and more particularly to FIGURES 1-10, a preferred means for producing stable elongated elements according to the instant inventive concept is designated generally by the reference numeral 20. Although, as has been mentioned hereinabove, certain of the basic features of this invention are equally applicable to the production of elongated elements, such as filter rods or the like, formed predominantly of particulate materials such as shown in parent application Ser. No. 351,162, the drawings illustrate the formation of such products from a continuous filamentary tow.

Further, while any of the frlamentary materials commonly used for producing elongated bodies such as filter rods and the like may be processed in accordance with this invention, such materials including the polyolens, e.g., polyethylene, the polyamides, eg., nylon, the polyesters, e.g., polyethylene terephthalate and the like, most products of this type are formed from cellulose acetate tows and the instant invention will be generally described with relation thereto. However, it is to be understood that similar products could be produced utilizing other materials in their entirety, or mixtures of such other materials with cellulose acetate. The use of materials other than cellulose acetate would necessitate only slight modifications in the processing techniques which would be obvious to those with ordinary skill in this art.

In the following description, however, it will be assumed that a continuous filamentary tow 22 has been formed from spinneret devices by any of the established techniques widely used in the industry today for formation of cigarette filter tows, and that the tow 22 has |been stored such as in a bale 24 or the like from which it can be withdrawn as desired for the further processing now to be described. Such a tow is generally referred to as a raw or untreated tow, and, as is well known, the fibers thereof are normally crimped and unbonded.

Known techniques can be initially followed in carrying out the instant invention, and as shown n FIGURE 1, the raw tow 22, in its crimped form, is passed through a conventional banding device 26 which comprises multiple jets disposed to blow air under pressure against the tow so as to separate the individual fibers thereof. The banded tow 2 may then be passed between pairs of rollers (not shown) to render the crimps therein of uniform character, following which the material passes through another banding device (not shown) similar to the device 26 which may be utilized to spread the tow into a relatively thin filamentary layer.

As shown in FIGURE l, the filamentary layer is then passed through a plasticizing device 28 wherein a suitable plasticizer such as triacetin, triethyl citrate or the like is sprayed by suitable jets onto one or both sides off the filamentary layer to form a plasticized tow 29. The quantity of plasticizer may vary, although the instant invention requires no more than and frequently less than, prior art techniques.

Any conventional feeding means such as the pair of rollers 3G, 32 may be utilized to deliver the plasticized tow 29 ot the endless belt 34 to be described in more detail hereinafter. Of course, it is to be understood that at least one of these rollers 3f) must be driven to effect the withdrawal of the raw tow 22 from the bale 24 and the feeding of the same to the belt 34 for carrying through subsequent processing stations.

The tow speed can be sufficiently great to provide satisfactory commercial production rates, Speeds of up to 200 meters per minute have been utilized with `acceptable product characteristics. Of course, the feeding rate must be correlated with the capacity of the various processing stations to insure that the resultant elements will have satisfactory properties. Such correlation can be readily accomplished by those with ordinary skill in the art.

If desired for special functional characteristics, an additive 35 may be substantially uniformly dispersed across at least the major portion of the width of the relatively thin layer of plasticized tow 29 by merely feeding the same from a dispensing means such as shown in dotted lines at 36 following the feeding roller 30. Such additives may be in the form of a liquid or in the form of a particulate material and may serve to modify the structural or functional properties of the final product. For example, various sorbent materials may be included to improve the filtration effected by the final product if the same is to be used as a cigarette or industrial filter. Exemplary of such materials are activated carbon, silica gel, alkali metal aluminosilicates, such as molecular sieves sold by Linde Company, a Division of Union Carbide Corporation, sucrose, activated alumina, volcanic ash, granular calcium carbonate, granular sodium carbonate, fullers earth, magnesium silicates, asbestos powder, metallic oxides such as iron oxide and aluminum oxide, metal treated carbon and the like. Additionally, where porosity or strength properties are a major consideration, metal fibers or even fibrous carbon can be included. Moreover, taste modifiers such as menthol or other similar materials may be incorporated :for obvious purposes. Additionally, certain particulate resinous materials such as'finely divided polyethylene or polypropylene may be included to improve the binding characteristics as well as the filtration properties of the final product. Mixtures of the above materials are also contemplated. Although it is important to recognize that while the additives and/or fillers listed above can be used if a particular effect is desired, they must be maintained in minor proportion in the overall construction, generally not more than about 30 percent by volume, if a structure having the basic characteristics of a continuous filamentary tow is desired.

The endless, flexible, porous belt 34 is utilized to define a continuous `material-forming and carrying surface and is orbitally trained about a group of path-defining rollers 38, 39, 40 and 42, at least one of which is driven by any conventional means (not shown). Additionally, a pair of tensioning rollers 44, 46 are included in the path of travel of the belt 34, the roller 44 being adjustable to facilitate maintaining a desired tension on the belt.

The preferred embodiments of this invention contemplate using a woven nylon belt preferably having a porosity such that the various gaseous mediums, eg., steam and air, to be utilized in treating the material therewithin in the processing stations to be described in more detail hereinafter, can pass through the belt and actually penetrate the material for optimum and substantially uniform results throughout the entire cross-section of the material. Preferably, of course, the pores in the belt are smaller than any of the material although the housings of the processing stations may assist -in supporting the belt to retain the material therewithin.

If desired, the belt may be provided with a lubricating or wear-resisting coating such as polytetrauoroethylene or a silicon emulsion. Such materials improve the water resistant properties of the belt as well as preventing adhesion between the belt fibers and the material carried thereby.

Referring now more particularly to FIGURES l-3 and 9, the plasticized tow 29, with or without additives, is fed onto the belt 34 by the rollers, 30, 32 in advance of a steam-treating station 48. The belt 34 is initially formed around the tow 29 by an elongated, open arcuate trough 50 (not shown in FIGURE l for illustrative clarity) and the tow 29 is guided into the belt 34 by an elongated, concavely curved tongue 52 fitting within the trough 50 and the belt 34. Portions of the steam-treating station 48 define an elongated bore 54 seen particularly in FIG- URE 9 which receives the belt 34 and the tow 22 from the trough 50 and the tongue 52. The bore 54 has a circumference so dimensioned with respect to the width of the lbelt as to form the belt into a substantially closed cross-section as it moves through the bore. The curve of the tongue 52 constantly decreases in cross-section and the smaller end of the tongue extends into the bore 54 as will be seen in FIGURE 9 until the belt 34 is substantially completely closed about the tow 29 to insure that the tow is guided into the closed belt. However, the tongue can terminate at the entrance of the bore, and the belt can there close. This forming of the belt and thereby the tow is accomplished at least partially in the initial portions of the steam-treating station 4S for convenience, but it will be understood that separate means may be included to effect this function, if desired.

Since there is some difficulty in forming the belt around the tow in a manner to provide a perfect meeting of the longitudinal edges of the belt, a longitudinal seam 56 will ordinarily result during this initial forming operation. In order to remove this seam by a pressing operation to be explained in more detail hereinafter and compensate for the change in cross-sectional shape of the tow resulting from the seam-removing operation, the tow is preferably initially formed into a slightly vertical, elongated or substantially vertical, elliptical shape as shown particularly in FIGURES 4 and 5. It is to be understood that this elongated shape and the seam resulting between the longitudinal edges of the belt are exaggerated in the drawings for illustrative convenience. In this regard, shims 58, 6G are shown in the housing 62 and insert 64 of the steam-treating station 48 as illustrated in FIGURE 4 to emphasize the slightly elongated construction of the confined area within the insert 64 which receives the belt 34 and the tow therewithin as the same passes through the steam-treating station. However, an elliptical bore can be used in insert e4. In either event, the width of the belt 34 is slightly less than the circumference of the elliptical confined area in the insert 64 whereby the longitudinal edges of the same will be slightly spread apart to facilitate the later seam-removing operation.

The insert 54 is carried within an elongated chamber 66 which receives steam from a source of the same (not shown) through a pair of oppositely disposed conduits 68, '70. A plurality of radially spaced passageways 72 are defined in the insert 64 communicating between the chamber 66 and the central area in which the belt 34 and tow therein are confined. Thus, steam under pressure is passed continuously and directly through the porous lsurface of the belt 34 and into the tow as the same is carried by the belt through the steam-treating station, to produce a steam-treated tow 73 generally of elliptical cross-section and having the longitudinal seam S6. In this manner the bonding constituents of the tow are activated by the steam while the tow is in a relaxed or substantially tensionless condition since it is being carried by the belt, rather than pulled through the processing station Aby some `forwardly-positioned pulling means.

The steam requirements can be varied by those with ordinary skill in the art to produce the desired activation of the bonding constituents of the tow, but, as will be seen from the subsequent examples, it has been found that with a tow feed rate of approximately 117 meters per minute and a tow cross-section of approximately 0.5 cm?, approximately 24 pounds per hour of steam provides satisfactory results.

Referring now particularly to FIGURES l and 6, the belt 34 with the steam-treated tow 73 therein moves from the steam-treating station 48 toward the cooling station 74. However, before entering the cooling station 74 a presser foot 76 engages the longitudinal seam 56 between the edges of the belt 34 to remove the same from the tow. The presser foot 76 is disposed in spaced relationship to an arcuate trough 7 3 formed at the entrance to the cooling station 74 so that the pressure resulting from engagement with the foot 76 simultaneously reforms the tow 73 into a substantially circular cross-section as will be seen in FIGURE 6 which corresponds to the desired cross-section of the final product. It is to be understood, once again, that the elements are somewhat exaggerated for illustrative purposes and that the presser foot 76 need not be, for example any more than approximately 'li" in cross-section under ordinary circumstances.

The housing 80 of the cooling station 74 defines a confined area in the form of an elongated cylindrical bore of a circular cross-section substantially corresponding to that of the final product as will be seen in FIGURE 7. The circumference of the confined area in the cooling station 74 is substantially equal to the width of the belt 34 whereby the longitudinal edges of the belt substantially meet during passage through the cooling station. It will be noted that the cooling station 74 is substantially longer than the steam-treating station 4S since it has been found that the production speed of the apparatus is dependent on the cooling capabilities in this station.

In order to provide for the most efficient cooling characteristics the station 74 is provided with a pair of elongated plenum chambers 82, 84 which communicate with the confined area through which the belt 34 and the tow therein passes, by means of a plurality of longitudinally spaced passageways 86, 38. The upper plenum chamber 82 receives air or other inert cooling gas, preferably under pressure, through a conduit 90 from a source (not shown). Similarly, the conduit 92 communicates with the plenum chamber 84 for removal of the air, vacuum being supplied at this point, if desired. In any event, it will be seen that the cooling gas is actually forced through the steamtreated tow 73 as the same is carried by the belt 34 through the cooling station 74. Once again, the drying of the tow and the setting of the bonding constituents of the same take place substantially in the absence of any tension.

As in the case of the steam requirements, the cooling gas may be varied within the skill of the ordinary artisan to insure that the desired characteristics in the final product will be obtained. It has been found, however, as will be seen from the subsequent examples, that with a tow feed and cross-section such as described with regard to the steam requirements, approximately 19.5 cubic feet per minute of air at room temperature, e.g. 70 to 85 F., and 261/2 p.s.i.g. produces satisfactory results.

At the Cooling station, the gas is passed into and through the formed material for essentially two purposes, namely, to cool and set or cure the previously activated bonding constituent and to remove excess moisture from the material. When the steam is passed to and into the tow to activate the bonding constituent, there is a tendency for the same to condense thus giving the product excessive moisture. Moreover, the steam expedites the action of the plasticizer on the tow-ie., it activates the bonding constituent so as to cause instantaneous bonding of the plasticized material. Thus, while the steam serves to efciently and uniformly activate the bonding constituent at high speeds, it has been found necessary at the cooling station to not only deactivate the bonding constituent but to also remove the excess moisture. In fact, the steam preferably causes full utilization of the plasticizer and the cooling gas then basically functions to remove excess moisture in the tow resulting from condensation of the steam and rigidify the rod being produced. Therefore, the terminology set the bonding constituent as used in the specification and claims is to be understood as including the operation just described when there is no plasticizer remaining in the tow to deactivate after the steam treatment.

With respect to the operations at both the steam treating and cooling stations, it is significant to note that the steam and air respectively pass to and into the tow without experiencing any significant or substantial flow resistance from the belt. The belt is thus suiiiciently porous, by virtue of its open mesh characteristics, to effectively permit vapor and gas passage therethrough without obstruction. This is to be distinguished from a fabric or closely woven belt wherein heat may be conducted therethrough, but obstruction and resistance is encountered in the passage of any gas or vapor therethrough.

The product 95 is peeled from the belt 34 as the same leaves the cooling station 74 and the belt 34 is substantially flattened and continuously orbited ove-r the path-defining and tensioning rollers 39, 4i), 44, 46, 42 and 38 to receive additional plasticized tow 29 in advance of the steami@ treating station 48. Thus, uninterrupted processing of the tow is effected by forming and carrying the same in the belt 34 with substantially no tension on the tow during the steam and cooling procedures.

The product is in the form of a stable, self-sustaining, elongated element shown illustratively as substantially circular in cross-section although it is to be understood that similar techniques could be utilized for the production of elements of substantially any other desired cross-section. The resultant product 95 has the individual filaments of the tow bonded to each other at spaced points to form a porous mass which, when used as a smoke filter, defines a plurality of tortuous paths for the passage of the smoke whereby effective filtration can be realized. The peripheral surface of the product 9S is textured as a result of an embossing operation produced by the surface configuration of the belt 34. This textured or embossed surface functions to prevent fraying of the individual filaments at the periphery of the product as well as providing the periphery with improved bonding properties for adhesively securing the same to a paper overwrap such as the tipping overwrap conventionally used in the formation of filter cigarettes or the like. This latter characteristic is in sharp contrast with the relatively smooth peripheral surface resulting from various prior art attempts at producing self-sustaining elongated bodies. Moreover, the open mesh, woven nature of the belt inherently produces an embossed pattern which is discontinuous to the longitudinal passage of smoke thereover when the element is incorporated into the filter section of a cigarette or the like. It will be readily seen that the particular design of the embossed surface may be varied at will be merely utilizing a belt having the desired surface configuration.

Although a tipping overwrap is conventionally utilized to attach a lter element such as the product of the instant invention to a tobacco section of a cigarette or the like, such an arrangement is to be distinguished from the utilization of a paper overwrap for the elongated element itself to provide dimensional stability. Such prior art paper overwraps are necessary during the processing cycle whereby, as pointed out earlier, pressure-drop characteristics of the product cannot be monitored `without removing sample portions from the production line. In contrast, since there is no overwrap utilized in the production of the continuous element according to the instant invention, the product 95 can be passed through a pressuredrop measuring means 96 of conventional design in order to continuously and directly monitor this property of the product without removing samples at selected intervals as has been necessary heretofore. By this technique, any conventional means shown schematically as a mechanical linkage by the dashed lines 9d may be utilized to translate the pressure-drop reading iliustratively shown on the gauge i639 into a control for the rate of feed Iof the tow 29 by, for example, the driven roller 3). In this manner, feeding of the tow 29 may be automatically and continuously varied in response to any changes in pressure-drop of the product 9S |whereby substantially constant pressuredrop characteristics may be maintained. In other words, if the pressure-drop of the product is found to be above the optimum value indicating that the product is too dense, the rate of feeding the tow into the steam-treating station 4S can be automatically reduced to compensate therefor. Similarly, if the pressure-drop characteristics are below the desired optimum, the tow feed can be increased. Although the means for effecting this continuous measuring of the pressure-drop properties of the product, and controlling the feed of the tow in response thereto have been shown `schematically in the drawings, actual mechanical and electrical devices to effect these operations can be readily designed by those lwith ordinary skill in the art.

The product 95, after having its pressure-drop properties measured, if desired, can then be severed by any conventional means shown schematically at 102 into individual segments 1M of at least substantially equal predetermined lengths for collection as in the collecting means 106. Once again, the continuous nature of the process can be retained by causing the severing means 102 to move with the product 95 in a well-known manner. If the product is to be utilized as a smoke filter, the segments 104 are generally cut into lengths equal to any multiple number of individual filter plugs which may be later `subdivided as is conventional in cigarette manufacture. The characteristic all-tow structure of the preferred product of the instant invention facilitates the severing technique in that it is unnecessary for the knife blade to engage materials of different characteristics such as the paper overwrap and tow core generally encountered in prior art products.

The use of a product segment 104 as a cigarette smoke filter is shown in FIGURE wherein a mass of tobacco 10S overwrapped with conventional cigarette paper 110 to form a tobacco section 111 is secured to the filter plug 104 by a conventional tipping overwrap 112. Preferably, the tipping overwrap 112 is adhesively secured substantially uniformly to the embossed peripheral surface of the filter plug 104 and includes an integral eX- tended portion 114 adhesively secured to the cigarette paper 110 at one end of the tobacco section 111. In this manner a single overwrap for the filter plug functions to attach the same to the tobacco section and simultaneously precludes channelling of smoke around the periphery of the iilter plug. As explained hereinabove, the embossed periphery of the filter plug 104 improves the bonding properties necessary for adhesively securing the same to the tipping overwrap 112 by providing a greatly increased surface area for reception of the adhesive material.

Although the instant inventive concept has been lgenerally described with reference to the production of cigarette filters or the like, it will be seen that the resultant product may have -many other uses, both related and unrelated to the smoke filtration of a filter cigarette. For example, the individual segments 104 may be utilized as industrial smoke filters or gas-liquid contact elements whereby the material being processed passes directly through the element as in a cigarette filter or, alternatively, into peripheral contact with a plurality of such elements as in the wellknown stacked columns. Further, the capillary properties of the product of the instant invention may be utilized, for example, in the use of the product elements as ink absorbers within dispensing containers such as the common felt marking devices. Other similar applications for such products will be Obvious to those with ordinary skill in the art and it is intended that the reference throughout this specification to smoke lters be considered merely as illustrative of the preferred use, rather than as limiting on the instant inventive concept.

Reference is now made particularly to FIGURES 11-16 wherein a modified lmeans according to the instant invention is designated generally by the reference numeral 130. This embodiment is directed to the production of stable elongated products having longitudinally spaced portions of different characteristics integrally connected by a central core formed from a continuous filamentary tow and utilizes, in effect, a double pass of the tow through two apparatus sections, each similar to the embodiment of FIGURE 1. In order to simplify an understanding of this modification, elements similar to those of FIGURE l forming the initial pass 132 have been designated in FIGURE l1 with the same reference numerals as in FIG- URE l followed by the suffix a and elements similar to those of FIGURE 1 forming the second pass 134 have been designated in FIGURE 1l with the same reference numerals as in FIGURE l followed by the suffix b.

The tow 29 which may have been banded, plasticized and treated with additive, if desired, as in FIGURE l, is fed onto the rst belt 34a in generally the same manner as the tow 29 was fed onto the belt 34 in the embodiment =of FIGURE 1. However, the belt 34a, as will be seen particularly in FIGURE l2, has alternate porous and nonporous sections 136, 138. Thus, on passage of the belt 34a through the first steam-treating station 48a after forming the belt about the tow 29, steam will pass only through the porous sections 136 of the belt and into contact with spaced portions of the tow 29 to decrease the diameter of the same as shown at 140 and to activate the bonding constituent in these spaced portions. Intermediate portions 142 of the tow 29 will not be contacted by the steam in the station 48a since these portions correspond to the non-porous sections 138 of the belt 34a.

Similarly, during passage of the belt 34a and the material confined therein through the first cooling station 74a, cooling gas is passed through the porous sections 136 of the belt 34a and into contact with the pcitions 140 of relativeiy smaller cross-section of the tow to set the bonding constituent of the same and thereby form a continuous intermediate element 145 having alternate portions of relatively large and relatively smaller cross-sections correspending to the porous and non-porous sections of the belt.

The confined areas within the first steam-treating station 48a and the first cooling station 74a are somewhat larger than the cross-section of the final product and the production of the intermediate element 145 need not be concerned with removal of the longitudinal seam or reforming of the same to a substantially circular cross-section since such operations will be effected during the second pass 134.

The intermediate element 145, after separation from the first belt 34a, is at least substantially confined by passing the same through an arcuately bent, elongated trough 146 to dene spaced annular areas surrounding the portions 140 of relatively smaller cross-section. The upper edges of the trough-defining element 146 are slightly spaced apart as shown, for example, in FIGURES 14 and 15, whereby the annular areas may be filled with at least one additive material including a bonding constitutent which will be activated during the second pass 134. Various methods and means may be utilized for forming and filling the annular areas, one technique being illustrated by the wheel 143 having peripheral pockets 150 for reception of the additive material 152 from a hopper 154 or the like. The pockets 150 are spaced in relation to the distance between the annular areas on the intermediate element 145 and the rate of rotation of the wheel 148 is correlated in any conventional manner with the rate of feed of the intermediate element 145 through the trough 146 whereby predetermined quantities of additive material 152 automatically fill the annular areas in the intermediate element 14S as will be seen particularly in FIG- URE 14.

It is to be understood that any desired additive material or combination of additive materials may be utilized to fill the annular areas in the intermediate area 145 so long as such additive materials include a bonding constituent which will be activated during the second pass 134. The preferred material, particularly for use in the production of cigarette filters or the like, is the combination of particles of activated carbon and particles of a thermoplastic material such as polyethylene utilized in the production of stable elongated bodies in the various parent applications referred to hereinabove. The polyethylene, being thermoplastic, will automtically be activated by Contact with steam during subsequent processing of the additive-containing intermediate element 156.

This element 156 is fed directly from the trough 146 onto the second belt 34h which is completely porous as is the belt 34 in the embodiment of FIGURE 1. In fact, the elements and processing techniques utilized in the second pass 134 of the embodiment of FIGURE l1 correspond substantially to the method and means shown and described with reference to FIGURE l. Thus, the additive-containing intermediate element 156, wrapped in the belt Sb is passed through the second steam-treating station 48b, preferably having a confined area of substanelement having alternate all-tow portions 160 spaced apart by portions having an annular section 162 of the additive material bonded together and to a tow core 164 which is integral with adjacent all-tow portions 160.

The elongated product 158 may be severed as in the embodiment of FIGURE 1 to form a plurality of individ- As shown in FIGURE 11, the segments 166 may contain a plurality of all-tow and additive-containing portions which are later subdivided to form individual, :integral dual filters such as shown in FIGURE 16 for use with a cigarette or the like in a conventional manner.

In order to further facilitate and understanding of the instant invention, the following examples are set forth intended merely as illustrative ditions, and not as limiting.

Example l shown in FIGURE l was followed utilizing a tow speed of approximately 117 meters per minute of raw cellulose acetate. After banding, approximately percent by weight of the tow of triacetin was sprayed onto the relatively thin layer of filaments and the plasticized tow was formed into a generally elliptical shape of a cross-section of approximately 0.5 cm.2. Steam at a rate of approximately 24 pounds per hour was passed into the plasticized tow in the steam-treating station following which the longitudinal seam formed in the tow was removed by pressing. The tow The procedure hours of storage were found to have the following weight characteristics and TABLE I Weight Ace- Plasti- Water, Total, Control (gram/10 tate,* eizer, percent percent rods) percent percent E As produced- 5. 95 82.3 l0. 0 7. 7 100. 0 After 24 hours.-. 5. 85 83.8 10. 2 6. 0 100. 0 After 72 hours.-. 5.77 84 6 10 0 5 4 10U. 0 *Including lubricant.

The above data shows a reduction in Water content during storage but the final moisture can be varied by modifying the characteristics of the cooling station as well as the relative humidity of the storage area.

14 Comparative test results between the product of the instant invention and ordinary paper overwrapped cellulose acetate rods of the prior art are as follows:

TABLE II Paper overwrapped Non-Wrapped Rods Rods Control Avg. Max. Min. Avg. Max. Min. K* Weight, gin/l0 rods 6. 5 6. 7 6. 4 5. 85 5. 95 5. 75 Pressure-drop, inches H2O 5. 3 6.1 4. 2 4. 8 4. Circurnference, mm 24. 6 24. 7 24. 5 24. 55 24. 65 24. 45 Length, mm 79. 7 80. 4 79. 3 79. 7 79. 8 79.5 Hardness 234 259 223 226 233 217 It will be seen from the above that, in substantially all instances, the non-Wrapped rods of the instant invention are more consistent in their properties than the paper overwrapped rods of the prior art. Other functional characteristics of the non-wrapped rods are at least comparable, and in many instances, improved, over prior art constructions.

Example 2 Example 1 is repeated with the dispersion of up to 30 percent by volume of finely divided flake carbon particles utilizing the technique shown at 36 in FIGURE 1. tration eiciency of the iinal product is improved because of the higher sorptive characteristics of the additive.

Example 3 taining approximately polyethylene. Treatment of the additivecontaining intermediate element in under similar conditions to those of Example 1, produced a self-sustaining, elongated, cylindrical element which, when severed into dual lters,

ing sense. Accordingly, what is claimed is:

1. dual lfilter comprising a first ethylene particles.

3. A cigarette comprising a tobacco section overpaper,

into a stable, porous, rod-like element, and a second section having a central core consisting essentially of a continuation of said tow in the central portion of said first section, and a stable, porous, annular sheath of an additive material bonded together and to said central core, and a tipping means securing said dual iilter to said tobacco section with said second section of said dual iilter interposed between said tobacco section and said first section of said dual lter.

4. The cigarette defined in claim 3 wherein said lamentary material is plasticized cellulose acetate and said additive material is carbon particles intermixed with polyethylene particles.

S. A iilter comprising a stable, porous, rod-like element consisting essentially of a tow of generally longitudinally extending, ilamentary material bonded together throughout to be self-sustaining, said rod-like element additionally including means on its peripheral surface rendering the same substantially resistent to filament separation, said rod-like element and means together having substantially uniform physical characteristics and porosity throughout any complete transverse cross-sectional area of the rod-like element and means, at least the predominant portion of the laments of said lamentary material each being of generally uniform diameter throughout its length and extending over at least the major extent of the length of said element.

6. The filter of claim 5 wherein said means on the peripheral surface of the rod-like element is an embossed pattern which is discontinuous to the longitudinal passage of smoke thereover when said element is incorporated into the lter section of a cigarette or the like.

7. A cigarette comprising a tobacco section overwrapped with cigarette paper and a filter section, said filter section including a stable, consisting essentially of a tow of generally longitudinally extending, ilamentary material bonded together throughout to be self-sustaining, said filter plug additionally iricluding means on its peripheral surface rendering the same porous, rod-like filter plug 3 substantially resistent to filament separation, said filter plug and means together having substantially uniform physical characteristics and porosity throughout any cornplete transverse cross-sectional area of the filter plug and means, at least the predominant portion of the filaments of said filamentary material each being of generally uni- -form diameter throughout its length and extending over `at least the major extent of the length of said filter plug, and a tipping overwrap adhesively secured substantially uniformly to said peripheral surface of said filter plug and including an integral extended portion adhesively secured to said cigarette paper at said one end of said tobacco section.

8. The cigarette of claim 7 wherein said means on the peripheral surface of said filter plug is an embossed pattern which is discontinuous to the longitudinal passage of smoke between said peripheral surface and said adhesively secured tipping overwrap.

References Cited by the Examiner UNiTED STATES PATENTS 2,688,380 9/1954 MacHenry 131-208 X 2,794,480 6/ 1957 Crawford et al 156-441 2,796,810 6/ 1957 Muller.

2,849,005 8/1958 Tucker et al 131--10 2,854,985 10/1958 Watkins 131--10 2,916,038 12/1959 Wade 131-10 3,079,978 3/1963 Cobb et al. 156-441 3,095,343 6/1963 Berger 156-180 3,106,501 10/1963 Cobb et al. 156-180 3,150,668 9/1964 Lassiter et al 131-10 FOREIGN PATENTS 5/1962 Canada. 3/1963 Canada. 

5. A FILTER COMPRISING A STABLE, POROUS, ROD-LIKE ELEMENT CONSISTING ESSENTAILLY OF A TOW OF GENERALLY LONGITUDINALLY EXTENDING, FILAMENTARY MATERIAL BONDED TOGETHER THROUGHOUT TO BE SELF-SUSTANING, SAID ROD-LIKE ELEMENT ADDITIONALLY INCLUDING MEANS ON ITS PERIPHERAL SURFACE RENDERING THE SAME SUBSTANTAILLY RESISTENT TO FILAMENT SEPARATION, SAID ROD-LIKE ELEMENT AND MEANS TOGETHER HAVING SUBSTANTIALLY UNIFORM PHYSICAL CHARACTERISTICS AND POROSITY THROUGHOUT ANY COMPLETE TRANSVERSE CROSS-SECTIONAL AREAS OF THE ROD-LIKE ELEMENT AND MEANS, AT LEAST 